The present invention relates to a force sensor, especially relates to a force sensor having a noise shielding layer configured on a top surface to screen noise signals caused by human body's touch.
The top force sensitive layer 112 and the bottom force sensitive layer 122 contact with each other when the force sensor is pressed. An electrical path is created among the top electrode 111, the top force sensitive layer 112, the bottom force sensitive layer 122, and the bottom electrode 121 and a corresponding force signal is generated for a control system (not shown) to process.
The disadvantage for the prior art is that a relative lower “signal-to-noise ratio” (S/N ratio) causes noise signals for an electronic system. A relative higher S/N ratio is preferred which eliminate noise signals a lot for an electronic system.
A material for the shielding layer is an electrical conductive material such as metal, conductive polymer, or ito (Indium Tin Oxide). The shielding layer can be formed with network or grid to save the conductive material.
For a modified force sensor (not shown), single layer of force sensitive layer can be adopted and configured between the top electrode 111 and the bottom electrode 121.
The force sensitive layer can be used for the present invention is made of a material selected from a group consisting of piezo-electric material, dielectric material, semi-conductive material, piezo-resistive material and piezo-capacitive material.
A material for the intermediate layer 35 is selected from a group consisting of an air space, piezo-capacitive material, and compressive-restorable dielectric material, so that the force sensor functions as a variable capacitor with AC power. Alternatively, a material for the intermediate layer 35 is selected from a group consisting of piezo-electric material, piezo-resistive material, compressible-restorable semiconductor polymer, so that that the force sensor functions as a variable resistor with DC power.
A material for the intermedia layer 45 is selected from a group consisting of piezo-capacitive material, and compressive-restorable dielectric material, so that the force sensor functions as a variable capacitor with AC power.
Alternatively, a material for the intermedia layer 45 is selected from a group consisting of piezo-electric material, piezo-resistive material, compressible-restorable semiconductor polymer, so that the force sensor functions as a variable resistor with DC power.
The auxiliary metal 512 is an independent metal layer to enhance an even distribution for electric field, and without connecting to any electrode.
A material for the intermediate layer 55 is selected from a group consisting of an air space, piezo-capacitive material, and compressive-restorable dielectric material. So that the force sensor functions as a variable capacitor with AC power.
Alternatively, a material for the intermediate layer 55 is selected from a group consisting of piezo-electric material, piezo-resistive material, compressible-restorable semiconductor polymer. So that the force sensor functions as a variable resistor with DC power.
Table 1 shows Electrode Configuration v Intermediate Layer choices for the force sensor of
The top electrode 61A is electrically coupled to ground, so that the top electrode 61A functions as a shielding layer and, in the meanwhile, functions as a counter electrode with respect to the bottom electrode 61B. i.e. the top electrode 61A and the bottom electrode 61B forms a variable capacitor force sensor. Capacitance exists between the top electrode 61A and the bottom electrode 61B as shown in heavy arrow in the
The variable resistor force sensor of
An air space or a compressible-restorable material can be used to replace the piezo capacitive material 62P.
While several embodiments have been described by way of examples, it will be apparent to those skilled in the art that various modifications may be configured without departs from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.
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